Featured Research

from universities, journals, and other organizations

Evolution Of The Human Appendix: A Biological 'Remnant' No More

Date:
August 21, 2009
Source:
Duke University Medical Center
Summary:
The lowly appendix, long-regarded as a useless evolutionary artifact, won newfound respect two years ago when researchers proposed that it actually serves a critical function. The appendix, they said, is a safe haven where good bacteria could hang out until they were needed to repopulate the gut after a nasty case of diarrhea, for example.

Normal location of the appendix relative to other organs of the digestive system (frontal view).
Credit: Wikimedia Commons

The lowly appendix, long-regarded as a useless evolutionary artifact, won newfound respect two years ago when researchers at Duke University Medical Center proposed that it actually serves a critical function. The appendix, they said, is a safe haven where good bacteria could hang out until they were needed to repopulate the gut after a nasty case of diarrhea, for example.

Now, some of those same researchers are back, reporting on the first-ever study of the appendix through the ages. Writing in the Journal of Evolutionary Biology, Duke scientists and collaborators from the University of Arizona and Arizona State University conclude that Charles Darwin was wrong: The appendix is a whole lot more than an evolutionary remnant. Not only does it appear in nature much more frequently than previously acknowledged, but it has been around much longer than anyone had suspected.

"Maybe it's time to correct the textbooks," says William Parker, Ph.D., assistant professor of surgical sciences at Duke and the senior author of the study. "Many biology texts today still refer to the appendix as a 'vestigial organ.'"

Using a modern approach to evolutionary biology called cladistics, which utilizes genetic information in combination with a variety of other data to evaluate biological relationships that emerge over the ages, Parker and colleagues found that the appendix has evolved at least twice, once among Australian marsupials and another time among rats, lemmings and other rodents, selected primates and humans. "We also figure that the appendix has been around for at least 80 million years, much longer than we would estimate if Darwin's ideas about the appendix were correct."

Darwin theorized that the appendix in humans and other primates was the evolutionary remains of a larger structure, called a cecum, which was used by now- extinct ancestors for digesting food. The latest study demonstrates two major problems with that idea. First, several living species, including certain lemurs, several rodents and a type of flying squirrel, still have an appendix attached to a large cecum which is used in digestion. Second, Parker says the appendix is actually quite widespread in nature. "For example, when species are divided into groups called 'families', we find that more than 70 percent of all primate and rodent groups contain species with an appendix." Darwin had thought that appendices appeared in only a small handful of animals.

"Darwin simply didn't have access to the information we have," explains Parker. "If Darwin had been aware of the species that have an appendix attached to a large cecum, and if he had known about the widespread nature of the appendix, he probably would not have thought of the appendix as a vestige of evolution."

He also was not aware that appendicitis, or inflammation of the appendix, is not due to a faulty appendix, but rather due to cultural changes associated with industrialized society and improved sanitation. "Those changes left our immune systems with too little work and too much time their hands – a recipe for trouble," says Parker.

That notion wasn't proposed until the early 1900's, and "we didn't really have a good understanding of that principle until the mid 1980's," Parker said. "Even more importantly, Darwin had no way of knowing that the function of the appendix could be rendered obsolete by cultural changes that included widespread use of sewer systems and clean drinking water."

Parker says now that we understand the normal function of the appendix, a critical question to ask is whether we can do anything to prevent appendicitis. He thinks the answer may lie in devising ways to challenge our immune systems today in much the same manner that they were challenged back in the Stone Age. "If modern medicine could figure out a way to do that, we would see far fewer cases of allergies, autoimmune disease, and appendicitis."

Colleagues who contributed to the study include lead author Heather Smith, of the Arizona College of Osteopathic Medicine; Rebecca Fisher, of Arizona State University; and Mary Lou Everett, Anitra Thomas and R. Randal Bollinger from the Department of Surgery at Duke.


Story Source:

The above story is based on materials provided by Duke University Medical Center. Note: Materials may be edited for content and length.


Cite This Page:

Duke University Medical Center. "Evolution Of The Human Appendix: A Biological 'Remnant' No More." ScienceDaily. ScienceDaily, 21 August 2009. <www.sciencedaily.com/releases/2009/08/090820175901.htm>.
Duke University Medical Center. (2009, August 21). Evolution Of The Human Appendix: A Biological 'Remnant' No More. ScienceDaily. Retrieved August 1, 2014 from www.sciencedaily.com/releases/2009/08/090820175901.htm
Duke University Medical Center. "Evolution Of The Human Appendix: A Biological 'Remnant' No More." ScienceDaily. www.sciencedaily.com/releases/2009/08/090820175901.htm (accessed August 1, 2014).

Share This




More Plants & Animals News

Friday, August 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Visitors Feel Part of the Pack at Wolf Preserve

Visitors Feel Part of the Pack at Wolf Preserve

AP (July 31, 2014) Seacrest Wolf Preserve on the northern Florida panhandle allows more than 10,000 visitors each year to get up close and personal with Arctic and British Columbian Wolves. (July 31) Video provided by AP
Powered by NewsLook.com
Florida Panther Rebound Upsets Ranchers

Florida Panther Rebound Upsets Ranchers

AP (July 31, 2014) With Florida's panther population rebounding, some ranchers complain the protected predators are once again killing their calves. (July 31) Video provided by AP
Powered by NewsLook.com
Dangerous Bacteria Kills One in Florida

Dangerous Bacteria Kills One in Florida

AP (July 31, 2014) Sarasota County, Florida health officials have issued a warning against eating raw oysters and exposing open wounds to coastal and inland waters after a dangerous bacteria killed one person and made another sick. (July 31) Video provided by AP
Powered by NewsLook.com
Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins